dp_add.c 4.3 KB

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  1. /* IEEE754 floating point arithmetic
  2. * double precision: common utilities
  3. */
  4. /*
  5. * MIPS floating point support
  6. * Copyright (C) 1994-2000 Algorithmics Ltd.
  7. *
  8. * This program is free software; you can distribute it and/or modify it
  9. * under the terms of the GNU General Public License (Version 2) as
  10. * published by the Free Software Foundation.
  11. *
  12. * This program is distributed in the hope it will be useful, but WITHOUT
  13. * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  14. * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
  15. * for more details.
  16. *
  17. * You should have received a copy of the GNU General Public License along
  18. * with this program; if not, write to the Free Software Foundation, Inc.,
  19. * 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20. */
  21. #include "ieee754dp.h"
  22. union ieee754dp ieee754dp_add(union ieee754dp x, union ieee754dp y)
  23. {
  24. int s;
  25. COMPXDP;
  26. COMPYDP;
  27. EXPLODEXDP;
  28. EXPLODEYDP;
  29. ieee754_clearcx();
  30. FLUSHXDP;
  31. FLUSHYDP;
  32. switch (CLPAIR(xc, yc)) {
  33. case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_SNAN):
  34. case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_SNAN):
  35. case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_SNAN):
  36. case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_SNAN):
  37. case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_SNAN):
  38. return ieee754dp_nanxcpt(y);
  39. case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_SNAN):
  40. case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_QNAN):
  41. case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_ZERO):
  42. case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_NORM):
  43. case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_DNORM):
  44. case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_INF):
  45. return ieee754dp_nanxcpt(x);
  46. case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_QNAN):
  47. case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_QNAN):
  48. case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_QNAN):
  49. case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_QNAN):
  50. return y;
  51. case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_QNAN):
  52. case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_ZERO):
  53. case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_NORM):
  54. case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_DNORM):
  55. case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_INF):
  56. return x;
  57. /*
  58. * Infinity handling
  59. */
  60. case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_INF):
  61. if (xs == ys)
  62. return x;
  63. ieee754_setcx(IEEE754_INVALID_OPERATION);
  64. return ieee754dp_indef();
  65. case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_INF):
  66. case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_INF):
  67. case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_INF):
  68. return y;
  69. case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_ZERO):
  70. case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_NORM):
  71. case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_DNORM):
  72. return x;
  73. /*
  74. * Zero handling
  75. */
  76. case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_ZERO):
  77. if (xs == ys)
  78. return x;
  79. else
  80. return ieee754dp_zero(ieee754_csr.rm == FPU_CSR_RD);
  81. case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_ZERO):
  82. case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_ZERO):
  83. return x;
  84. case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_NORM):
  85. case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_DNORM):
  86. return y;
  87. case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM):
  88. DPDNORMX;
  89. /* FALL THROUGH */
  90. case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_DNORM):
  91. DPDNORMY;
  92. break;
  93. case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_NORM):
  94. DPDNORMX;
  95. break;
  96. case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_NORM):
  97. break;
  98. }
  99. assert(xm & DP_HIDDEN_BIT);
  100. assert(ym & DP_HIDDEN_BIT);
  101. /*
  102. * Provide guard,round and stick bit space.
  103. */
  104. xm <<= 3;
  105. ym <<= 3;
  106. if (xe > ye) {
  107. /*
  108. * Have to shift y fraction right to align.
  109. */
  110. s = xe - ye;
  111. ym = XDPSRS(ym, s);
  112. ye += s;
  113. } else if (ye > xe) {
  114. /*
  115. * Have to shift x fraction right to align.
  116. */
  117. s = ye - xe;
  118. xm = XDPSRS(xm, s);
  119. xe += s;
  120. }
  121. assert(xe == ye);
  122. assert(xe <= DP_EMAX);
  123. if (xs == ys) {
  124. /*
  125. * Generate 28 bit result of adding two 27 bit numbers
  126. * leaving result in xm, xs and xe.
  127. */
  128. xm = xm + ym;
  129. if (xm >> (DP_FBITS + 1 + 3)) { /* carry out */
  130. xm = XDPSRS1(xm);
  131. xe++;
  132. }
  133. } else {
  134. if (xm >= ym) {
  135. xm = xm - ym;
  136. } else {
  137. xm = ym - xm;
  138. xs = ys;
  139. }
  140. if (xm == 0)
  141. return ieee754dp_zero(ieee754_csr.rm == FPU_CSR_RD);
  142. /*
  143. * Normalize to rounding precision.
  144. */
  145. while ((xm >> (DP_FBITS + 3)) == 0) {
  146. xm <<= 1;
  147. xe--;
  148. }
  149. }
  150. return ieee754dp_format(xs, xe, xm);
  151. }